Originally Posted by
cxwrench
Lots of people do, especially if I maintain their bike(s). If you ride regularly (3-5 days a week) once a year is the longest you should go between replacing them. The main reason you replace the cables is because you're replacing the housing. That's where all of the wear that impacts shifting performance takes place. Replacing the cables alone won't get you anywhere. On a road bike this also gives you the chance to replace bar tape. That **** gets nasty and you can get some substantial corrosion on the bars/shifter clamps. I just did cables/housing/tape on a guys bike and it was disgusting. Co-workers could smell it as they walked by. No one wants to be around that much less have to touch it. Take care of your equipment. I've got a story about a guy that ended up dead because he completely ignored his commute bike and his bars broke due to corrosion.
It's amazing that while few people will go to the dentist right after eating a sleeve of Oreos, they expect the LBS mechanic to service their filty neglected bike.
If your housings are worn down enough to affect shifting, a cable and housing change is long overdue. In fact, it's doubtful that a cable run on STI shifters will last anywhere near that long considering STI shifters' appetite for cables.